A liquid chromatograph (LC) becomes an analysis device necessary for researching and developing organic chemistry and is introduced widely in laboratories at universities, laboratories in chemical companies and the like. In the natural world, materials of single components are little and most of materials are mixtures of complex components. The liquid chromatograph is a device that can separate the complex components into individual components, using a liquid as a measurement sample. The complex components are separated into the individual components, so that calculation of a content of each component and extraction and elimination of a specific component are enabled. When these components are detected, types of measured samples may be large and detectors for the liquid chromatograph may be diversified. Even as for detectors to which representative optical technology is applied, there are an ultraviolet detector, a visible detector, a diode array detector, a differential refractive index detector, an electric conductivity detector, a fluorescent detector, and a chemiluminescence detector.
In addition, when molecular weights of the components separated by the liquid chromatograph are measured, a mass spectrometer (MS) is used. A device to which the liquid chromatograph and a mass spectrometry unit are coupled is called a liquid chromatograph/mass spectrometer (LC/MS). The mass spectrometer ionizes a sample solution and introduces the ions into the mass spectrometer in at vacuum state. The mass spectrometer separates the ions by electric and magnetic actions according to a mass/charge ratio (m/z) and detects the individual ions. A mass spectrum in which a horizontal axis shows the mass/charge ratio and a vertical axis shows detection strength is obtained. Because a charged component (ion) molecule is directly detected, sensitivity is high as compared with the detector using the optical technology. In addition, there is a superior characteristic in that a structure of the component can be determined because the molecular weight can be measured. For this reason, the liquid chromatograph/mass spectrometer is used in wide fields such as development and quality control of pharmaceutical products, environment measurement, and foods. Recently, measurement of a blood biomarker from the knowledge obtained from a biomarker search, measurement of protein generated from genetic information, and structure analysis of the protein after a modification in a cell attract attention.
A use environment: of the liquid chromatograph/mass spectrometer also spreads from the university or company laboratories to clinical laboratories in hospitals and the liquid chromatograph/mass spectrometer changes from a device used by a specialist in mass spectrometry to a device used by a specialist in other field. For this reason, a device that has convenience and high durability as well as high sensitivity to be one of characteristics of the mass spectrometry and a device that can perform maintenance easily are demanded.
The mass spectrometers are largely divided into devices mainly performing quantitative analysis and devices mainly performing qualitative analysis. As a representative mass spectrometer that mainly performs the quantitative analysis, there is a triple quadrupole mass spectrometer (hereinafter, referred to as the triple-QMS) that has a plurality of quadrupole mass spectrometry units provided inside. Because the triple-QMS has a characteristic that specific ions of a measurement sample can be continuously detected, quantitative analysis performance is high. Meanwhile, as a mass spectrometer that mainly performs the qualitative analysis, there is a flight time type mass spectrometry unit (hereinafter, referred to as the TOF/MS). Measurement ions are flown in vacuum, a time until the ions arrive at a detector is measured, and a molecular weight is measured. Because a width of a mass/charge ratio observed is large and a mass spectrum with high resolution is easily obtained, qualitative analysis performance becomes high.
In the mass spectrometer, an internal state becomes a vacuum state, electrodes having various shapes are disposed, and ions introduced into the mass spectrometer are controlled and separated by an electric field. For example, the quadrupole mass spectrometry unit is also called a Q mass (QMF) or a mass filter and includes four cylindrical electrodes. The cylindrical electrodes are combined by positioning a center of a circle at a vertex of a square. A positive/negative direct current and a high frequency alternating-current voltage are applied to the electrodes adjacent to the fixed cylindrical electrode to be superimposed. When the ions having the charge pass through the electrodes, the ions pass through the electrodes while vibrating and only a certain ion vibrates stably according to the voltage and the frequency and passes through the electrodes. Meanwhile, the vibration of the other ions increases during passing through the electrodes and the ions collide the electrodes and cannot pass through the electrodes. The mass spectrum is obtained by changing the high frequency alternating-current voltage linearly while maintaining a ratio of the direct current and the alternating-current voltage constantly.
A device in which one quadrupole mass spectrometry unit (QMF) is mounted in the mass spectrometer is called a single quadrupole mass spectrometer (hereinafter, referred to as the Single-QMS). Because the mass spectrometer has a small size, the mass spectrometer is relatively cheap and is used widely for gas analysis. Meanwhile, the resolution of the mass spectrum is not high as about a 1 mass-charge ratio width. In addition, when the mass spectrometer is used as the detector of the liquid chromatograph, sensitivity is deteriorated because a noise derived from the solvent is observed at a low mass-charge ratio.